Nomenclature	GPR62	GPR63	GPR65	GPR68	GPR75
HGNC, UniProt	GPR62, Q9BZJ7	GPR63, Q9BZJ6	GPR65, Q8IYL9	GPR68, Q15743	GPR75, O95800
Endogenous ligand	–	–	Protons	Protons	–
Comments	–	sphingosine 1‐phosphate and dioleoylphosphatidic acid have been reported to be low affinity agonists for GPR63 [1394] but this finding was not replicated in an arrestin‐based assay [2093].	GPR4, GPR65, GPR68 and GPR132 are now thought to function as proton‐sensing receptors detecting acidic pH [396, 1704]. Reported to activate adenylyl cyclase; gene disruption leads to reduced eosinophilia in models of allergic airway disease [1000].	GPR68 was previously identified as a receptor for sphingosylphosphorylcholine (SPC) [2068], but the original publication has been retracted [2067]. GPR4, GPR65, GPR68 and GPR132 are now thought to function as proton‐sensing receptors detecting acidic pH [396, 1704]. A family of 3,5‐disubstituted isoxazoles were identified as agonists of GPR68 [1617].	CCL5 (CCL5, P13501) was reported to be an agonist of GPR75 [816], but the pairing could not be repeated in an arrestin assay [1785].